Several homologous series of ultra-pure allergens will be isolated from pollen extracts of species of the ragweed tribe (Ambrosieae) and the grass family (Gramineae). In particular, we will concentrate on the purification of allergens of relatively simple molecular structure (5,000-8,000 daltons), in order to facilitate structure-function studies of human immune response to these allergens. The prototype is short ragweed allergen Ra5 (mol. wt. 5,000 daltons) where we have already established an extremely striking association with HLA-Dw2 in responder subjects. These studies will be extended to include Ra5 molecules from at least three further ragweed species where the same or different HLA-D associations may exist. Then, we will conduct analogous studies using other homologous series of allergens from ragweed and grass pollens, especially molecules in Gramineae species which may be structurally similar to Ra5. We propose to identify determinants recognized at the B-cell level by human IgE and IgG antibodies on various allergens, especially Ra5 and grass Group I homologues. These studies will utilize both selective chemical modification of allergenic/antigenic determinants and Fab fragments of mouse monoclonal antibodies to block antigen binding of IgE and IgG antibodies toward specific sites on the molecules, using a large number of allergic sera. Monoclonal antibodies will also be used to facilitate purification of a series of immunologically closely related molecules (e.g. grass Group I). Human IgE and IgG responses to these related molecules will then be analyzed in relation to amino acid sequence differences. A particular asset in carrying out these studies will be the availability of two well-characterized populations: ca. 350 local clinic paties and ca. 500 subjects from an epidemiologic-genetic study of human immune response to allergens, which has been in progress during the past 6 years.